<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android" > <group android:checkableBehavior="single"> <item android:id="@+id/calibrate" android:title="@string/action_calibrate" android:showAsAction="ifRoom|withText" /> <item android:id="@+id/preview_mode" android:title="@string/preview_mode"> <menu> <group android:checkableBehavior="single"> <item android:id="@+id/calibration" android:title="@string/calibration" android:checked="true" /> <item android:id="@+id/undistortion" android:title="@string/undistortion" /> <item android:id="@+id/comparison" android:title="@string/comparison" /> </group> </menu> </item> </group> </menu>